U.S. patent application number 09/444517 was filed with the patent office on 2001-11-22 for double-chuck mechanical pencil.
Invention is credited to EBINUMA, TADAYOSHI, KAGEYAMA, HIDEHEI, MITSUYA, YOSHIHIDE.
Application Number | 20010043832 09/444517 |
Document ID | / |
Family ID | 26459770 |
Filed Date | 2001-11-22 |
United States Patent
Application |
20010043832 |
Kind Code |
A1 |
KAGEYAMA, HIDEHEI ; et
al. |
November 22, 2001 |
DOUBLE-CHUCK MECHANICAL PENCIL
Abstract
A double-chuck mechanical pencil has an outer tube, a tip
fitting provided in the front of the outer tube, a tip chuck
located at the tip of the tip fitting for holding a writing
substance (e.g., a lead) and urged rearward in the axial directed,
and a delivery chuck for delivering the lead. At least one of the
tip chuck and the delivery chuck is formed of a synthetic resin
material including polyoxymethylene.
Inventors: |
KAGEYAMA, HIDEHEI;
(KAWAGOE-SHI, JP) ; MITSUYA, YOSHIHIDE;
(KAWAGOE-SHI, JP) ; EBINUMA, TADAYOSHI;
(KAWAGOE-SHI, JP) |
Correspondence
Address: |
MCGINN & GIBB, PLLC
8321 OLD COURTHOUSE ROAD
SUITE 200
VIENNA
VA
22182-3817
US
|
Family ID: |
26459770 |
Appl. No.: |
09/444517 |
Filed: |
November 22, 1999 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09444517 |
Nov 22, 1999 |
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09075335 |
May 11, 1998 |
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6039485 |
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Current U.S.
Class: |
401/67 ; 401/65;
401/87; 401/94 |
Current CPC
Class: |
B43K 21/22 20130101 |
Class at
Publication: |
401/67 ; 401/65;
401/87; 401/94 |
International
Class: |
B43K 021/16 |
Foreign Application Data
Date |
Code |
Application Number |
May 13, 1997 |
JP |
9-122683 |
Jun 24, 1997 |
JP |
9-166901 |
Claims
What is claimed is:
1. A double-chuck mechanical pencil, comprising: an outer tube; a
tip fitting provided in a front of the outer tube, and including a
tip; a tip chuck, located at the tip of the tip fitting, for
holding a lead and urged rearwardly in an axial direction; and a
delivery chuck for delivering a lead, the delivery chuck being
movable forwardly to deliver a lead after the tip chuck has been
moved forwardly to release the lead, wherein at least one of the
tip chuck and the delivery chuck is formed of a synthetic resin
material.
2. A double-chuck mechanical pencil according to claim 1, wherein
said synthetic resin material comprises polyoxymethylene.
3. A double-chuck mechanical pencil according to claim 1, wherein
said synthetic resin material comprises polyoxymethylene in which
glass fibers are mixed.
4. A double-chuck mechanical pencil according to claim 3, wherein
substantially about 5 to about 20 wt % of glass fibers are mixed
with polyoxymethylene.
5. A double-chuck mechanical pencil according to claim 4, wherein
substantially about 15 wt % of glass fibers are mixed with
polyoxymethylene.
6. A double-chuck mechanical pencil according to claim 1, wherein
said synthetic resin material comprises polyoxymethylene in which a
lubricant is mixed.
7. A double-chuck mechanical pencil according to claim 1, wherein
the at least one of the tip chuck and the delivery chuck that is
formed of said synthetic resin material comprises a plurality of
chuck elements obtained by dividing a head of the chuck along a
circumferential direction, and wherein a circumferential gap,
formed between adjacent chuck elements when the plurality of chuck
elements are allowed to approach one another such that a contour of
an external shape of the chuck elements forms a true circle as seen
from the axial direction, is no more than substantially about 0.15
mm.
8. A double-chuck mechanical pencil according to claim 1, wherein
the tip chuck and the delivery chuck each comprise a plurality of
chuck elements that are formed by dividing the tip chuck and the
delivery chuck, respectively, along a circumferential direction
from their head to rear side and that are mutually separated and
opposed, and wherein an axial length of the separated and opposed
chuck elements of the tip chuck is shorter than that of the
delivery chuck.
9. A double-chuck mechanical pencil according to claim 1, wherein
the tip and delivery each include a holding section for holding the
lead, and wherein an axial length of the holding section of said
tip chuck for holding the lead inside thereof is longer than that
of the delivery chuck.
10. A double-chuck mechanical pencil according to claim 1, wherein
a protrusion is provided at an end of said tip chuck, and the end
at which the protrusion is pressed in a tip of a through-hole in an
axial cylinder disposed inside the tip fitting so as to penetrate
the tip of the tip fitting, and wherein a staged surface that abuts
the protrusion and a larger-diameter portion that is separated from
the protrusion behind the staged surface are formed at the tip of
the through-hole.
11. A double-chuck mechanical pencil according to claim 1, wherein
at least the tip chuck is formed of the synthetic resin
material.
12. A double-chuck mechanical pencil according to claim 11, wherein
said tip chuck is colored depending on a diameter of the lead.
13. A double-chuck mechanical pencil according to claim 11, wherein
a staged surface for abutting a surface of the tip of said tip
fitting is provided on said tip chuck, and wherein an end of said
tip chuck is coupled to a tip of a lead delivery mechanism disposed
inside the tip fitting so as to penetrate the tip of the tip
fitting.
14. A double-chuck mechanical pencil according to claim 11, wherein
said tip chuck is formed by combining a plurality of separate chuck
members together.
15. A double-chuck mechanical pencil according to claim 11, wherein
said tip chuck has a plurality of chuck elements for holding the
lead, and said plurality of chuck elements are mutually extended in
an outer-diameter direction when the tip chuck is molded, and
wherein ends of the chuck elements are pressed in a tip of a
central hole in an axial cylinder disposed inside the outer tube to
reduce a mutual extension of tips of the chuck elements, to prevent
the lead from falling freely when the tip chuck advances.
16. A double-chuck mechanical pencil according to claim 15, further
comprising a ring member positioned on an outer circumferential
surface of said tip chuck for limiting a radial extension of the
chuck elements.
17. A double-chuck mechanical pencil according to claim 15, further
comprising: a protrusion that is pressed in the central hole in
said axial cylinder and is formed on the outer circumferential
surface of ends of said chuck elements; and a notch, formed in a
side end of the chuck elements, for deforming the protrusion in an
inner-diameter direction thereof.
18. A double-chuck mechanical pencil according to claim 11, wherein
said tip chuck has a plurality of chuck elements for holding the
lead, and said plurality of chuck elements are mutually extended in
an outer-diameter direction when the tip chuck is molded, and
wherein a ring member for adjusting a radial extension of the chuck
elements is positioned on an outer circumferential surface of the
tip chuck to reduce a mutual extension of the tips of the chuck
elements to prevent the lead from falling freely when the tip chuck
advances.
19. A double-chuck mechanical pencil according to claim 18, further
comprising: a notch, formed in a side end of the chuck elements,
for deforming the tip chuck in an inner-diameter direction thereof
so as to correspond to the positioning of said ring member.
20. A writing instrument, comprising: a fitting including a tip; a
first chuck located at the tip of the fitting for holding a writing
substance and urged in a first direction; and a second chuck for
delivering the writing substance, the second chuck being movable in
a second direction, to deliver the writing substance after the
first chuck has been moved in the second direction to release the
writing substance, wherein at least one of the first chuck and the
second chuck is formed of a synthetic resin material.
21. A writing instrument according to claim 20, wherein said
synthetic resin material comprises polyoxymethylene.
22. A writing instrument according to claim 21, wherein said
synthetic resin material comprises polyoxymethylene in which glass
fibers are mixed.
23. A writing instrument according to claim 22, wherein
substantially about 5 to about 20 wt % of glass fibers are mixed
with polyoxymethylene.
24. A writing instrument according to claim 23, wherein
substantially about 15 wt % of glass fibers are mixed with
polyoxymethylene.
25. A writing instrument according to claim 20, wherein said
synthetic resin material comprises polyoxymethylene in which a
lubricant is mixed.
26. A writing instrument according to claim 20, wherein the at
least one of the first chuck and the second chuck that is formed of
said synthetic resin material comprises a plurality of chuck
elements, and wherein a circumferential gap, formed between the
adjacent chuck elements when the plurality of chuck elements are
allowed to approach one another, is no more than substantially
about 0.15 mm.
27. A writing instrument according to claim 20, wherein the first
chuck and the second chuck each comprise a plurality of chuck
elements that are mutually separated and opposed, and wherein an
axial length of the separated and opposed chuck elements of the
first chuck is set to be shorter than that of the second chuck.
28. A writing instrument according to claim 20, wherein said first
chuck includes a holding section for holding the writing substance,
and wherein an axial length of the holding section of said first
chuck is longer than that of the second chuck.
29. A writing instrument according to claim 20, wherein at least
the first chuck is formed of the synthetic resin material.
30. A writing instrument according to claim 20, wherein said first
chuck is formed by combining a plurality of separate chuck members
together.
31. A writing instrument according to claim 30, further comprising
a ring member positioned on an outer circumferential surface of
said first chuck for limiting a radial extension of the chuck
elements.
32. A writing instrument according to claim 31, further comprising:
a protrusion formed on the outer circumferential surface of an end
of said chuck elements; and a notch, formed in a side end of the
chuck elements, for deforming the protrusion in an inner-diameter
direction thereof.
33. A writing instrument according to claim 20, wherein said first
chuck has a plurality of chuck elements for holding the lead, and
wherein a ring member for adjusting a radial extension of the chuck
elements is positioned on an outer circumferential surface of the
first chuck to reduce a mutual extension of tips of the chuck
elements to prevent the lead from falling freely when the first
chuck advances.
34. A writing instrument according to claim 33, further comprising:
a notch, formed in a side end of the chuck elements, for deforming
the first chuck in the inner-diameter direction thereof so as to
correspond to the positioning of said ring member.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a writing instrument, and
more particularly to a double-chuck mechanical pencil having a tip
chuck located at the tip of a tip fitting to hold a lead and a
delivery chuck for delivering the lead.
[0003] 2. Description of the Related Art
[0004] A conventional example of a mechanical pencil having two
chucks is described in Japanese Utility Model Application Laid-Open
No. 4-119435.
[0005] Generally, a tip chuck and a delivery chuck of such a
mechanical pencil are formed of a metal material. To manufacture
the tip and delivery chucks, an approximately cylindrical metal
material must be sawed, rubbed, and cut by a cutter to divide the
material into a plurality of chuck elements (e.g., two or three),
which then are subjected to secondary processing such as burr
removal.
[0006] Subsequently, the chuck elements of the delivery chuck must
be extended outwardly, while the chuck elements of the tip chuck
must be subjected to secondary processing such as narrowing because
excessively-opened chuck elements cause a lead to fall (e.g.,
drop-out from the pencil) when the tip chuck is moved forward to
release the lead. Thus, manufacturing such a mechanical pencil is
labor-intensive and costly.
SUMMARY OF THE INVENTION
[0007] In view of the foregoing and other problems of the
conventional writing instruments, an object of the present
invention is to provide a double-chuck mechanical pencil that
reduces manufacturing costs.
[0008] To achieve this and other objects, a double chuck mechanical
pencil according to the present invention includes an outer tube, a
tip fitting provided in the front of the outer tube, a tip chuck
located at the tip of the tip fitting for holding a lead and urged
rearwardly in the axial direction, and a delivery chuck for
delivering a lead, the delivery chuck being movable forwardly to
deliver a lead after the tip chuck has been moved forward to
release the lead, wherein at least one of the tip chuck and the
delivery chuck is formed of a synthetic resin material.
[0009] By forming the chucks of a synthetic resin material into a
desired shape, secondary processing such as burr removal or the
widening or narrowing of the tip of the chuck, or the like, is
unnecessary, thereby reducing manufacturing costs.
[0010] Preferably, the synthetic resin material includes
polyoxymethylene, and preferably consists essentially of
polyoxymethylene. This composition provides a mechanically strong
chuck with high abrasion resistance.
[0011] Additionally, preferably, the synthetic resin material
includes, and preferably consists essentially of, polyoxymethylene
in which glass fibers are mixed. This composition provides elastic
chucks which reduce damage to leads being held by the chucks,
thereby preventing the leads from being broken. Appropriate
elasticity can be provided for the chucks by mixing
polyoxymethylene with substantially about 5 to about 20 wt %, and
preferably, substantially about 15 wt % of glass fibers.
[0012] Alternatively, the synthetic resin material includes, and
preferably consists essentially of polyoxymethylene in which a
lubricant is mixed. This composition enables smooth sliding between
the tip fitting and the tip chuck, and between the delivery chuck
and its peripheral members. Specific lubricants include molybdenum,
silicon, tungsten, and/or the like.
[0013] Additionally, preferably, at least the one of the tip and
delivery chucks that is formed of the synthetic resin material
includes a plurality of chuck elements obtained by dividing the
head of the chuck along the circumferential direction, and the
circumferential gap between the adjacent chuck elements, formed
when the plurality of chuck elements are allowed to approach one
another such that the contour of the external shape of the chuck
elements forms a true circle as seen from the axial direction, is
substantially about 0.15 mm or less.
[0014] In the conventional chuck formed of a conventional metal
material, an approximately cylindrical chuck is divided into a
plurality of chuck elements by a cutter, so that the
circumferential gap between the chuck elements cannot be reduced
below the edge width of the cutter (e.g., about 0.15 to 0.2 mm).
However, by forming the chucks of the synthetic resin, the chucks
of the present invention can be formed into desired sizes by
molding. Accordingly, the circumferential gap between the plurality
of chuck elements formed when the chuck elements are allowed to
approach one another such that the contour of the external shape of
the chuck elements forms a true circle as seen from the axial
direction, can be set to a small value (e.g., substantially about
0.15 mm or less). Consequently, the area in which the lead held by
the chuck elements contacts the chuck elements can be increased to
allow the leads to be reliably sandwiched by the chuck
elements.
[0015] Additionally, preferably, the tip and delivery chucks
include a plurality of chuck elements that are formed by dividing
the chucks along the circumferential direction from a first to a
second side (e.g., their head to rear side) and that are mutually
separated and opposed, and the axial length of the separated and
opposed chuck elements of the tip chuck is set to be shorter than
that of the delivery chuck.
[0016] This configuration enables the mutual extension of the chuck
elements of the tip chuck to be reduced below that of the delivery
chuck. Thus, if the lead becomes short and is located in front of
the delivery chuck, then the inventive mechanical pencil provides a
lead holding force sufficient to prevent the chuck elements of the
tip chuck from being excessively opened to prevent the lead from
falling (e.g., dropping out) even when the tip chuck is releasing
the lead.
[0017] Furthermore, preferably, the axial length of the holding
section of the tip chuck for holding the lead inside thereof is set
to be longer than that of the delivery chuck. This configuration
enables the lead to be firmly sandwiched by the tip chuck, and to
prevent the lead from being broken.
[0018] Additionally, preferably, a protrusion is provided at the
rear end of the tip chuck, and the rear end at which the protrusion
is provided, is pressed in the tip of a through-hole in an axial
cylinder disposed inside the tip fitting so as to penetrate the tip
of the tip fitting. A staged surface that abuts the protrusion and
a larger-diameter portion that is separated from the protrusion
behind the staged surface may be formed at the tip of the
through-hole. The protrusion of the tip chuck engages the staged
surface of the axial cylinder to prevent the tip chuck from
slipping out from the axial cylinder. Additionally, since the
larger-diameter portion that is separated from the protrusion of
the tip chuck is formed on the axial cylinder, a radial load from
the protrusion is precluded from being constantly applied to the
axial cylinder, thereby to prevent the axial cylinder from being
damaged.
[0019] Preferably, at least the tip chuck is formed of the
synthetic resin material. This composition reduces material costs
and manufacturing processes, thereby reducing manufacturing
costs.
[0020] The color of the tip chuck formed of the synthetic resin
material may vary depending on the diameter of the lead. This
configuration enables the user to determine quickly and simply a
lead diameter compatible with the mechanical pencil merely from the
color of the tip chuck.
[0021] Additionally, a staged surface for abutting the tip surface
of the tip fitting is provided on the tip chuck, and the rear end
of the tip chuck can be coupled to the tip of a lead delivery
mechanism disposed inside the tip fitting, so as to penetrate the
tip of the tip fitting. When the tip fitting is disassembled from
the outer tube, the staged surface of the tip chuck abuts the tip
surface of the tip fitting to hinder the tip chuck and the lead
delivery mechanism from slipping out from the tip fitting, thereby
preventing the parts from being disconnected and lost. Since the
tip chuck is formed of the synthetic resin material, the staged
surface can be formed simply by molding.
[0022] Additionally, the tip chuck can be formed by combining a
plurality of separate chuck members together. This configuration
enables the tip chuck to be formed simply to desired sizes by
molding each chuck member into a desired shape.
[0023] Additionally, the tip chuck formed of the synthetic resin
material has a plurality of chuck elements that hold the lead. The
plurality of chuck elements are mutually extended in the
outer-diameter direction when the molding of the tip chuck is
finished, and the rear ends of the chuck elements may be pressed in
the tip of a central hole in the axial cylinder disposed inside the
outer tube to reduce the mutual extension of the tips of the chuck
elements to provide a holding force sufficient to prevent the lead
from falling freely (e.g., dropping out from the pencil) when the
tip chuck advances. This configuration eliminates secondary
processing such as burr removal or the narrowing of the tip of the
chuck to reduce manufacturing processes and costs. Even when the
lead becomes shorter than the length between the tip and delivery
chucks, the lead is prevented from falling because the mutual
extension of the chuck elements is reduced, thereby to provide a
holding force sufficient to prevent the lead from falling freely
(e.g., dropping out) when the tip chuck advances to release the
lead.
[0024] Additionally, optionally, a ring-like member is positioned
on the outer circumferential surface of the middle of the tip chuck
to limit the radial extension of the chuck elements. After the
ring-like member has restricted the radial extension of each chuck
element, the tip chuck can be pressed in the axial cylinder to
facilitate the press-in operation. Furthermore, optionally, a
protrusion that is pressed in the central hole in the axial
cylinder is formed on the outer circumferential surface of the rear
end of the chuck elements, and a notch for deforming the protrusion
in the inner-diameter direction is formed in the side end of the
chuck elements. This configuration can facilitate the operation for
pressing the chuck elements in the axial cylinder.
[0025] According to another aspect of the present invention, the
tip chuck formed of the synthetic resin material has a plurality of
chuck elements that hold the lead. The plurality of chuck elements
are mutually extended in the outer-diameter direction with respect
to each other when the molding of the tip chuck is finished, and a
ring-like member for hindering the radial extension of the chuck
elements may be installed on the outer circumferential surface of
the tip chuck to reduce the mutual extension of the tips of the
chuck elements, to provide a holding force sufficient to prevent
the lead from falling freely when the tip chuck advances. By
forming the tip chuck of the synthetic resin material, material
costs can be reduced, and the tip chuck can be molded in the
desired form. This configuration also eliminates secondary
processing such as burr removal or the narrowing of the tip of the
chuck to reduce manufacturing processes and costs. Even when the
lead becomes shorter than the length between the tip and delivery
chucks, the lead is prevented from falling because the mutual
extension of the chuck elements is reduced, thereby to provide a
holding force sufficient to prevent the lead from falling freely
when the tip chuck advances to release the lead.
[0026] Additionally, optionally, a notch for deforming the tip
chuck in the inner-diameter direction is formed in the side end of
the chuck elements so as to correspond to the installation of the
ring-like member. This configuration facilitates the operation for
installing the ring-like member on the tip chuck.
[0027] The present disclosure relates to subject matter contained
in Japanese Patent Application HEI 9-122683, filed May 13, 1997 and
from Japanese Patent Application HEI 9-166901, filed Jun. 24, 1997,
which are expressly incorporated herein by reference in their
entirety.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] The foregoing and other objects, aspects and advantages will
be better understood from the following detailed description of
preferred embodiments of the invention with reference to the
drawings, in which:
[0029] FIG. 1 is a longitudinal sectional view showing an
embodiment of a double-chuck mechanical pencil according to the
present invention;
[0030] FIGS. 2(A) and 2(B) are a front view and a longitudinal
sectional view, respectively, of a delivery chuck 16;
[0031] FIGS. 3(A) and 3(B) are a front view and a longitudinal
sectional view, respectively, of a tip chuck 30;
[0032] FIG. 4 is a side view showing the delivery chuck 16 in its
free condition;
[0033] FIG. 5 is an enlarged view of a tip in FIG. 1;
[0034] FIGS. 6(A)-6(C) illustrate another tip chuck 30, with
[0035] FIG. 6(A) being a front view of the tip chuck,
[0036] FIG. 6(B) being a longitudinal sectional view, respectively
of the tip chuck, and
[0037] FIG. 6(C) being a plan view of a chuck member forming the
tip chuck;
[0038] FIG. 7 is a longitudinal sectional view showing a second
embodiment of a double-chuck mechanical pencil according to the
present invention;
[0039] FIG. 8 is an enlarged sectional view showing a tip chuck and
the front of an axial cylinder of the double-chuck mechanical
pencil in FIG. 7;
[0040] FIG. 9 is an enlarged sectional view of the tip chuck in
FIG. 7 before it is pressed in the axial cylinder;
[0041] FIG. 10 corresponds to FIG. 8 and shows a third embodiment
of the present invention;
[0042] FIG. 11 corresponds to FIG. 8 and shows a fourth embodiment
of the present invention; and
[0043] FIG. 12 corresponds to FIG. 8 and shows a fifth embodiment
of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE
INVENTION
[0044] Embodiments of this invention are described in detail with
reference to the drawings. FIG. 1 is a longitudinal sectional view
showing a first embodiment of a double-chuck mechanical pencil
according to the present invention.
[0045] In FIG. 1, an outer tube 10 is shown, and a tip fitting 12
is secured by screwing or adhesion, and is provided in the front of
the outer tube 10.
[0046] A lead delivery mechanism 14 is disposed inside the outer
tube 10 and the tip fitting 12. The lead delivery mechanism 14
includes a delivery chuck 16 for delivering a lead, a chuck ring 18
fitted on the head of the delivery chuck 16 to tighten the delivery
chuck 16, a sleeve 20 that abuts an end (e.g., the rear end) of the
chuck ring 18, a lead tank (e.g., storage) 22 connected to the
delivery chuck 16, a first chuck spring 24, interposed between an
end (e.g., the front end) of the lead tank 22 and an end (e.g., the
front end) of the sleeve 20, for urging the delivery chuck 16
rearward in an axial direction via the lead tank 22, an axial
cylinder 26 into which the delivery chuck 16 and the chuck ring 18
are built, a rubber member 27 disposed in the axial cylinder 26 for
holding a lead using frictional force, and a rear sleeve 28
connected to the rear end of the lead tank 22 by being press-fitted
therein (e.g., a pressing-in operation).
[0047] The front end of the sleeve 20 abuts a staged (e.g.,
stepped) portion 26b provided on the inner circumferential surface
of the middle of the through-hole 26a of the axial cylinder 26, and
a protrusion 20a from the sleeve 20 engages an engagement hole 26c
provided in the circumferential surface of the rear of the axial
cylinder 26, for integrally connecting together the axial cylinder
26 and the sleeve 20. The axial cylinder 26 and the sleeve 20 may
be integrally formed as a unitary member.
[0048] A tip chuck 30 is pressed in the tip of the through-hole 26a
in the axial cylinder 26, so as to penetrate the tip of the tip
fitting 12.
[0049] Specifically, as shown in FIG. 5, a protrusion 30a is formed
on the outer circumference of the rear of the tip chuck 30, while a
staged (e.g., stepped) surface 26d is formed on the front of
circumferential surface of the through-hole 26a in the axial
cylinder 26. A portion of the axial cylinder 26 which is located
behind the staged surface 26d forms a larger-diameter portion 26e
having a larger inner diameter than a portion of the axial cylinder
which is located in front of the staged surface 26d.
[0050] The protrusion 30a is pressed in the tip of the through-hole
26a through the tip of the axial cylinder 26, to engage the staged
surface 26d after passing surface 26d, and the larger-diameter
portion 26e forms an escape portion for the protrusion 30a beyond
the staged surface 26d, to prevent the protrusion 30a from
interfering with the larger-diameter portion 26e in the radial
direction. This configuration prevents a radial load from
protrusion 30a from being applied to the axial cylinder 26 to
prevent the axial cylinder 26 from being damaged.
[0051] A second chuck spring 32 is interposed between the tip of
the axial cylinder 26 and a staged portion 12a provided inside the
tip fitting 12, to urge the tip chuck 30 rearwardly in the axial
direction via the axial cylinder 26. The second chuck spring 32 is
selected to have a smaller elastic resilient force than that of the
first chuck spring 24. A staged surface 30b facing rearwardly is
further formed on the tip chuck 30, and is pressed by the urging
force of the second chuck spring 32 against a tip surface 12b of
the tip fitting 12 that faces forward. The staged surface 30b
interferes with (e.g., abuts) the tip surface 12b of the tip
fitting 12, to prevent the tip chuck 30 and the lead delivery
mechanism 14 from being disconnected even when the tip fitting 12
is removed from the outer tube 10.
[0052] As further shown in FIG. 1, the outer circumferential
surface of a rear sleeve 28 and the inner circumferential surface
of the outer tube 10 are locked using a key and a key groove.
Furthermore, an eraser holding cylinder 40 is forcibly connected to
the rear end of the rear sleeve 28, and an eraser 42 is detachably
fitted in the eraser holding cylinder 40. A knock cap 44 covers the
eraser, a tail closure 46 is provided, a clip 48 is sandwiched
between the tail closure 46 and the rear end of the outer tube 10,
and a rubber gripper 50 is wound around a gripping portion of the
outer tube 10.
[0053] In the present invention, the delivery chuck 16 and the tip
chuck 30 of the present invention are formed of a synthetic resin
material, instead of a metal material as in the conventional
mechanical pencils. A specific synthetic resin material includes,
and preferably consists essentially of, polyoxymethylene (POM) that
has a relatively high abrasion resistance and mechanical
strength.
[0054] Additionally, by mixing substantially about 5 to about 20 wt
%, and more preferably substantially about 15 wt % of glass fibers
in polyoxymethylene, the elasticity can be increased to reduce
damage to the lead when the lead is held by the tip chuck 30 and
the delivery chuck 16.
[0055] Furthermore, the mixture of a lubricant such as molybdenum,
silicon, tungsten, and/or the like can avoid abrasion caused by
sliding between the tip chuck 30 and the tip fitting 12, or between
the delivery chuck 16 and the chuck ring 18. Such a lubricant may
be coated on metal chucks, or may be mixed in the synthetic resin
material for molding, eliminating a coating operation and the
like.
[0056] Additionally, the tip chuck 30 can be colored by mixing a
colorant in the synthetic resin material as desired. For example,
tip chucks for a 0.5 mm lead diameter are colored brown, tip chucks
for a 0.3 mm lead diameter are colored yellow, and tip chucks for a
0.7 mm lead diameter are colored blue according to ISO9175-1. Such
coloring is helpful for the user to quickly determine a lead
diameter compatible with a particular mechanical pencil.
[0057] FIGS. 2(A) and 2(B) are a front view and a longitudinal
sectional view, respectively, of the delivery chuck 16. FIGS. 3(a)
and 3(b) are a front view and a longitudinal sectional view,
respectively, of the tip chuck 30. Each of the figures shows the
respective chuck 16, 30 in its closed state.
[0058] As shown, the delivery chuck 16 and the tip chuck 30 each
may have a Y-shaped configuration including a plurality (e.g.,
three) chuck elements 17 and a plurality (e.g., three) chuck
elements 31, respectively, that are obtained by dividing the
respective chuck into three portions (e.g., chuck elements) along
the circumferential direction from a first end to a second end
(e.g., front to rear).
[0059] As shown in FIGS. 2(A)-(B) and 3(A)-(B), the axial length L2
of the divided chuck elements 31 of the tip chuck 30 is set to be
shorter than that L1 of the divided chuck elements 17 of the
delivery chuck 16. This configuration enables the mutual extension
of the chuck elements 31 of the tip chuck 30 to be reduced below
the mutual extension of the divided chuck elements 17 of the
delivery chuck 16. Thus, even while the tip chuck 30 is releasing a
lead 52, the chuck elements 31 of the tip chuck 30 can maintain a
holding force sufficient to prevent the free falling of the lead 52
without being too widely opened.
[0060] Additionally, holding sections 16a and 30c extending in
parallel in the axial direction are provided inside of the delivery
chuck 16 and the tip chuck 30 for holding the lead 52,
respectively. The axial length L4 of the holding section 30c of the
tip chuck 30 is set to be longer than axial length L3 of the
holding section 16a of the delivery chuck 16. This configuration
enables the tip chuck 30 to sandwich the lead 52 more firmly than
the delivery chuck 16, thereby allowing the tip to hold the lead 52
firmly to prevent the lead from being broken during writing.
Additionally, the sandwiching force applied to the lead by the
inventive chucks 16, 30 being formed of synthetic resin material is
expected to be weaker than that applied by the conventional metal
chucks, and thus the lengths L3 and L4 should be set larger than
when metal chucks are used.
[0061] Furthermore, the gap among the three adjacent chuck elements
17 of the delivery chuck 16 and the three adjacent chuck elements
31 of the tip chuck 30 as shown in FIGS. 2(A) and 3(A),
respectively, formed when the elements are allowed to approach one
another, is set to be as close to zero as possible (e.g.,
substantially about 0.15 mm or less), so that the contour of the
external shape of the chuck elements 17 and 31 forms a true circle
as seen from the axial direction. Such a preferred gap dimension
increases the area in which the lead held by the chuck elements 17
and 31 contacts the chuck elements 17 and 31, thereby allowing the
lead to be reliably sandwiched by the chuck elements 17 and 31.
[0062] To mold each of the delivery chuck 16 and the tip chuck 30,
the chuck elements 17 and 31 must be molded in advance so as to be
opened in the radial direction with respect to each other so that
they can release the lead 52.
[0063] For example, FIG. 4 is a side view of the delivery chuck 16
in its free state, such that the chuck elements 17 are extended
radially. The mutual extension of the chuck elements 17 and 31 may
be adjusted taking into consideration, for example, the shrinkage
factor of the resin after molding has finished and the return of
the chuck elements 17 and 31 in the radially internal direction
caused by a return spring force after molding. Such molding enables
the chuck elements 17 and 31 to be formed so as to have appropriate
mutual extensions and appropriate axial lengths so that a very
small gap is formed among them when they are allowed to approach
one another.
[0064] Consequently, secondary processing and the like, as in
fabrication of the conventional metal chuck, are eliminated to
reduce the number of required steps. Additionally, since desired
shapes can be obtained by molding, the protrusion 30a and staged
surface 30b of the tip chuck 30 can be formed simply.
[0065] FIGS. 6(A)-6(C) show another embodiment of the tip chuck 30.
The tip chuck 30 is formed by combining a plurality of (e.g., two)
chuck members 30-1, 30-1 together in the vertical direction, and a
protrusion 30-1a and a hole 30-1b are formed in the connecting
surface of each chuck member 30-1, as shown in FIG. 6(C). The
integral tip chuck 30 is formed by fitting the protrusion 30-1a
from one of the chuck members 30-1 in the hole 30-1b in the other
chuck member 30-1. An end (e.g., the rear end) of the chuck is
integrally pressed in the axial cylinder 26. The rears of the chuck
members 30-1, 30-1 are integrally connected together, whereas the
tips are tilted so as to be mutually separated, thereby to form the
two chuck elements 31, 31 that are divided along the
circumferential direction. The axial length of the chuck elements
31, 31 is shown by L2 in FIG. 6(B).
[0066] Thus, by forming the tip chuck 30 of the plurality of chuck
members 30-1, 30-1 and individually forming each chuck member 30-1
so as to have a desired shape, the length L1 and the mutual
extension of the chuck elements 31 can be set to desired values.
Additionally, the gap among the chuck elements 31 formed when the
elements are allowed to approach each other can be set simply and
easily to be as close to zero as possible, so that the contour of
the external shape of the chuck elements 31, 31 forms a true circle
when viewed from the axial direction.
[0067] It is noted that, while the above chuck members 16, 34 have
been described as each having a plurality of chuck elements (e.g.,
two or three chuck elements in the embodiments described), the
chuck member could have more than three portions with suitable
design modifications, as would be known to one of ordinary skill in
the art taking the present specification as a whole.
[0068] To form the above-described pencil, the lead delivery
mechanism 14 is assembled and then inserted into the tip fitting 12
via the second chuck spring 32, and the rear end of the tip chuck
30 is pressed in the axial cylinder 26 in the lead delivery
mechanism 14. Then, after the tip fitting 12 has been secured to
the outer tube 10, and the eraser holding cylinder 40 is pressed in
the rear sleeve 28. Finally, the other parts are assembled
together.
[0069] To deliver the lead 52 in the above-described double-chuck
mechanical pencil, the knock cap 44 is knocked (e.g., actuated or
depressed) to compress the second chuck spring 32 using the elastic
resilient force smaller than that of the first chuck spring 24,
thereby moving the lead delivery mechanism 14 forward. The tip
chuck 30 correspondingly advances and protrudes from the tip
fitting 12 to release the lead 52.
[0070] When the knock cap 44 is further actuated, the first chuck
spring 24 of the lead delivery mechanism 14 is compressed to move
the delivery chuck 16 forward to deliver the lead 52. Even when the
lead becomes shorter than the length between the tip chuck 30 and
the delivery chuck 16, actuating/depressing the knock cap 44 causes
the tip chuck 30 to release the lead so as not to drop the lead.
Further actuating/depressing the knock cap 44 causes the subsequent
lead moved forward by the delivery chuck 16 to press and deliver
the preceding lead. This operation enables even a short lead to be
used for writing. When the user releases the knock cap 44, the
urging force of the first and second chuck springs 24 and 32 causes
the delivery and tip chucks 16 and 30 to move backward in the axial
direction to sandwich the lead again. Then, the mechanical pencil
is ready for writing.
[0071] Since the delivery and tip chucks 16 and 30 are formed of
the synthetic resin material, although the lead 52 is sandwiched by
both chucks, the elasticity of the synthetic resin material allows
the lead to be held softly and prevents the lead from being
damaged.
[0072] Additionally, despite the use of two chucks, material costs
and manufacturing processes can be reduced, thereby to reduce
manufacturing costs by forming the chucks of the synthetic resin
material.
[0073] Although this embodiment has been described in conjunction
with the formation of both the delivery and tip chucks of the
synthetic resin material, only one of the delivery and tip chucks
may be formed of the synthetic resin material. However, forming
only one of the delivery and tip chucks of the synthetic resin
material may be somewhat disadvantageous in terms of manufacturing
costs, as compared to the above-described embodiment. Particularly,
if only the delivery chuck is formed of the synthetic resin
material, the amount of the return of the lead tends to be large
when the chuck moves backward. Thus, if only on chuck is to be
formed of the synthetic resin material, it is preferable that only
the tip chuck be formed of the synthetic resin material.
[0074] Second Embodiment
[0075] FIG. 7 is a longitudinal sectional view of a second
embodiment of a double-chuck mechanical pencil according to the
present invention. In FIG. 7, the same elements as in IG. 1 have
the same reference numerals, and, for brevity, their detailed
description is omitted.
[0076] A tip chuck 34 is pressed in the tip of the central hole 26a
in the axial cylinder 26 so as to penetrate the tip of the tip
fitting 12. A staged surface 35b facing rearward is formed at the
tip of the tip chuck 34, and is pressed against the tip surface 12b
of the tip fitting 12 that faces forwardly due to the urging force
of the second chuck spring 32. Due to the interference (e.g.,
abutment) of the staged surface 35b with the tip surface 12b of the
tip fitting 12, the tip chuck 34 and the lead delivery mechanism 14
are prevented from being mutually disconnected even when the tip
fitting 12 is removed from the outer tube 10.
[0077] Like the tip chuck 30, the tip chuck 34 is formed of a
synthetic resin material preferably including, and even more
preferably consisting essentially of, polyoxymethylene (POM) having
a high abrasion resistance and mechanical strength, instead of a
metal material. Preferably, substantially about 5 to about 20 wt %,
and even more preferably, substantially about 15 wt %, of glass
fibers can be mixed in the polyoxymethylene to improve elasticity
and to reduce damage to the lead when it is tightened.
[0078] Furthermore, the mixture of a lubricant such as molybdenum,
silicon, and/or tungsten can avoid abrasion caused by sliding
between the tip chuck 34 and the tip fitting 12. Such a lubricant
is coated on metal chucks, but it can be mixed in the synthetic
resin material for molding the inventive chuck, thereby eliminating
a costly coating operation or the like.
[0079] Additionally, as described above with the tip chuck 34 can
be colored by mixing a colorant in the synthetic resin material as
required. For example, tip chucks for a 0.5 mm lead diameter are
colored brown, tip chucks for a 0.3 mm lead diameter is colored
yellow, and tip chucks for a 0.7 mm lead diameter are colored blue
according to ISO9175-1. Such coloring is helpful for the user to
quickly determine a lead diameter compatible with a particular
mechanical pencil.
[0080] FIG. 8 is an enlarged sectional view showing the tip chuck
34 and the axial cylinder 26, and FIG. 9 is an enlarged sectional
view of the tip chuck 34 before the tip chuck 34 is pressed in the
axial cylinder 26. The tip chuck 34 has a Y-shape and includes a
plurality of (three) chuck elements 35 that are obtained by
dividing the respective chuck into three portions along the
circumferential direction from a first end to a second end (e.g.,
head to rear), as shown in FIG. 9.
[0081] When the molding of the tip chuck 34 is finished, the chuck
elements 35 of the tip chuck 34 are mutually extended in the radial
direction. This configuration prevents a core pin used to mold the
divided chuck elements 35 from becoming too thin. Even during a
time of the tip chuck 34 releasing the lead, the chuck elements 35
of the tip chuck 34 require a holding force sufficient to prevent
the free falling of the lead without being too widely opened. Thus,
the rear end of the chuck elements 35 is pressed in the tip of the
central hole 26a in the axial cylinder 26 to reduce the mutual
extension of the chuck elements 35 so that their tips can provide a
holding force sufficient to prevent the lead from falling freely
when the tip chuck 34 advances.
[0082] Specifically, the protrusion 35a from the outer
circumferential surface of the rear end of the chuck elements 35 is
pressed in the tip of the central hole 26a through the tip of the
axial cylinder 26, and engages the staged surface 26d formed in the
front of the inner circumferential surface of the central hole 26a
in the axial cylinder 26. Additionally, a staged surface 35d formed
on the outer circumferential surface in the middle of the chuck
elements 35 and facing rearward abuts the tip of the axial cylinder
26. To facilitate this press-in operation, a notch 35e for
deforming the protrusion 35a in the inner-diameter direction is
formed at the side end of each chuck element 35.
[0083] By adjusting the positions of the staged surfaces 35d and
26d and the protrusion 35a, the length of the chuck elements 35
that is inserted into the central hole 26a in the axial cylinder 26
is set at an appropriate value to provide the appropriate mutual
extension of the chuck elements 35. Alternatively, suitable
spreading of the chuck elements 35 may be provided by arraying the
axial cylinder 26 to have the central hole 26a with a suitable
diameter. As shown in FIG. 8, a circumferential gap "d" is shown
between the lead holding sections 35c representing the mutual
extension of the lead holding sections 35c at the tip of the chuck
elements 35 when the tip chuck 34 is pressed in the axial cylinder
26. The size of the gap "d" further decreases to reliably tighten
the lead when the tip chuck 34 moves backward to its rear-most
position, into the tip fitting 12, as shown in FIG. 7.
[0084] In a mechanical pencil of the above configuration, the lead
is delivered when the knock cap 44 is knocked (e.g., actuated) as
in the first embodiment. When the lead becomes shorter than the
length between the tip chuck 34 and the delivery chuck 16,
actuating the knock cap 44 causes the tip chuck 34 to advance and
protrude from the tip fitting 12 to release the lead. However, the
lead is prevented from falling because the mutual extension of the
chuck elements 35 is so small that the lead holding sections 35c at
the tip of the chuck elements 35 provide holding force sufficient
to prevent the lead from falling freely, as described above.
[0085] Further actuating the knock cap 44 causes the subsequent
lead moved forward by the delivery chuck 16 to press and deliver
the preceding lead held by the tip chuck 34. Hence, since the lead
is simply held by the chuck elements 35 so as not to fall freely,
the lead can be delivered smoothly without being damaged. When the
user releases the knock cap 44, the urging force of the first and
second chuck springs 24 and 32 causes the delivery and tip chucks
16 and 34 to move backward in the axial direction to sandwich the
lead again. Then, even a short lead can be used for writing.
[0086] Third Embodiment
[0087] FIG. 10 shows a third embodiment of the present invention,
and corresponds to FIG. 8. Before pressing the tip chuck 34 in the
axial cylinder 26, a ring 33 (a ring-like member) is installed on
the outer circumferential surface of the tip chuck 34. That is,
before pressing the tip chuck 34 into the axial cylinder 26, the
ring 33 is fitted on the tip chuck 34 from its rear until it abuts
the staged surface 35d, thereby to limit the radial extension of
each chuck element 35 in the tip chuck 34. This makes the press-in
operation easier.
[0088] Fourth Embodiment
[0089] FIG. 11 shows a fourth embodiment of the present invention,
and corresponds to FIG. 8. A ring 36 (a ring-like member) is
installed on the outer circumferential surface of the middle of the
chuck elements 35' of a tip chuck 34', a plurality of small
protrusions 35f are formed on the same surface in the axial
direction at a specified interval, and recessed portions 36a for
fitting on the small protrusions 35f are formed on the inner
circumferential surface of the ring 36.
[0090] Since a notch 35e allows the tip chuck 34' to be deformed in
the inner-diameter direction, the ring 36 can pass over the small
protrusion 35f, and its recessed portion 36a can be fitted on any
small protrusion 35f to lock the ring at any of the plurality of
positions in the axial direction. The axial position of the ring 36
can be adjusted to reduce the mutual radial extension of the lead
holding sections 35c at the tip of the chuck elements 35', to allow
the lead holding sections 35c to provide holding force sufficient
to prevent the lead from falling freely even when the tip chuck 34'
advances to protrude from the tip fitting 12.
[0091] Fifth Embodiment
[0092] FIG. 12 shows a fifth embodiment of the present invention,
and corresponds to FIG. 8. The tip of the axial cylinder 26 is
extended to form an extension 26e, and a protrusion 35g is formed
on the outer circumferential surface of the middle of each chuck
element 35' of a tip chuck 34" so that the extension 26e can press
the protrusions 35g. This configuration reduces the mutual radial
extension of the lead holding sections 35c at the tip of the chuck
elements 35" of the tip chuck 34" to allow the lead holding
sections 35c to provide holding force sufficient to prevent the
lead from falling freely even when the tip chuck 34" advances to
protrude from the tip fitting 12.
[0093] With the above-described embodiments of the present
invention, an inexpensive double-chuck mechanical pencil is
provided having a tip chuck located at the tip of a tip fitting for
holding the lead, and a delivery chuck for delivery a lead. At
least one of the tip chuck and the delivery chuck is made from a
synthetic resin material, thereby providing many of the advantages
discussed above.
[0094] While the principles of the invention have been described
above in connection with specific embodiments, and particular
modifications thereof, it is to be clearly understood that this
description is made only by way of example and not as a limitation
on the scope of invention. Thus, while the invention has been
described in terms of several preferred embodiments, those skilled
in the art will recognize that the invention can be practiced with
modification within the spirit and scope of the appended
claims.
* * * * *